Download chronic congestive heart failure.

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CHEMICAL CHARACTERIZATION OF CARDIAC MYOSIN FROM
NORMAL DOGS AND FROM DOGS WITH CHRONIC
CONGESTIVE HEART FAILURE
By JAMES 0. DAVIS, WILLIAM R. CARROLL, MARY TRAPASSO AND
NICHOLAS A. YANKOPOULOS WITH THE SURGICAL ASSISTANCE OF
ALFRED CASPER
(From the Section on Experimental Cardiovascular Disease, Laboratory of Kidney and
Electrolyte Metabolism, National Heart Institute, and the Section on Physical
Biochemistry, Laboratory of Physical Biology, National Institute of
Arthritis and Metabolic Diseases, Bethesda, Md.)
(Submitted for publication January 18, 1960; accepted March 31, 1960)
The size and chemical nature of the myosin
molecule have been studied extensively in enzyme
preparations obtained from skeletal muscle (1-7),
but a paucity of data is available on cardiac myosin.
Furthermore, different values for the molecular
weight of cardiac myosin have been reported.
Olson (8) reported a value of 223,000 for the
molecular weight of cardiac myosin whereas Gergely and Kohler (9) presented evidence that
myosin from cardiac muscle has a molecular
weight of 500,000, which is similar to that obtained during the most recent observations on
skeletal muscle myosin (4-7).
It has been suggested that the cardiac myosin
molecule is altered in cardiac failure to form a
stable aggregate of the basic monomer and that
abnormal myosin prevents the formation of normal
cardiac actomyosin (8). On the contrary, considerable evidence has been adduced that actomyosin from the failing heart is normal (10). The
present observations were undertaken to determine
the molecular size and chemical nature of normal
cardiac myosin and to compare these data with
results obtained on cardiac myosin from dogs with
chronic congestive heart failure.
METHODS
Muscle was obtained from the hearts of 12 normal
dogs, 11 dogs with right-sided cardiac failure secondary
to surgically-induced tricuspid insufficiency and pulmonic
stenosis, one dog with naturally occurring right- and
left-sided congestive failure and 3 dogs with chronic
ascites produced by constriction of the thoracic inferior
vena cava. The techniques used for the surgical procedures have been described previously (11-13). On the
day of sacrifice, studies were conducted to determine the
physiological state of the animals. All measurements of
cardiovascular pressures were made in trained unanesthetized dogs; the methods have been described previously
(13). The methods for Na balance measurements are
described elsewhere (1 1, 12); Na intake was 60 mEq
per day.
Cardiac muscle was obtained by anesthetizing the
animals lightly with intravenous sodium pentobarbital,
opening the chest quickly and excising the beating heart.
The heart was washed with cold water and placed in a
container with chipped ice. The right and left ventricular
walls were separated from the septum. Since only rightsided heart failure was present in dogs with tricuspid
insufficiency and pulmonic stenosis (13), muscle from the
right and from the left ventricles of these dogs was extracted separately for myosin. The left ventricle only
was used for preparation of myosin from the one dog with
naturally occurring right- and left-sided cardiac failure
and from the dogs with constriction of the thoracic inferior vena cava. Myosin was extracted from combined
right and left ventricles of normal dogs.
Myosin was prepared by the method of Gergely (14).
The extraction of myosin was begun immediately after
obtaining heart muscle. Since the yield of myosin was
low, all of the right or left ventricular muscle masses was
used. To obtain enough myosin for diffusion measurements, in some instances the right ventricles from 2 dogs
were combined for extraction and the left ventricles from
the same animals were extracted as one preparation. The
procedure to be described for the extraction of myosin
applies for a quantity of 75 g of cardiac muscle. If less
muscle was available, the volumes of the extracting media
were adjusted accordingly. The entire extraction procedure was carried out at 0° to 5° C.
Seventy-five g of heart muscle was ground with a meat
grinder and extracted with 300 ml of a salt solution by
stirring for 45 minutes. The salt solution contained 0.3
M KCI, 0.2 M potassium phosphate buffer (pH 6) and
0.02 M sodium pyrophosphate; the final pH of the solution was adjusted to 6.2 with KOH. The muscle extract
was squeezed through cheesecloth and the residue discarded. The extract was centrifuged at 2,000 rpm in a
Lourdes model AT centrifuge for 30 minutes. To precipitate the myosin, 10 volumes of glass distilled water
were added to each volume of the supernatant. The
precipitate of myosin was allowed to settle for at least
1 hour and the supernatant was siphoned off. The remaining myosin solution was centrifuged at 8,000 rpm in
the Lourdes centrifuge for 10 minutes. The supernatant
was discarded and the residue was dissolved in 2.4 M
1463
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1464
DAVIS, CARROLL, TRAPASSO AND YANKOPOULOS
TABLE I
Physiological data on experimental animals at the time of sacrifice
Dog
no.
Initial
body
wt
kg
1
2
3
4
5
6
7
8
9
10
11
X
18.3
21.5
20.5
17.0
19.0
18.9
18.5
25.0
20.5
19.0
18.6
19.8
Time
after
last
operation
Duration
of
ascites
Volume
of
ascites
Renal
Na
excretion
Plasma
Na
Plasma
K
Mean right
atrial
pressure
Ct
Et
mm water
L
mEqiday mEq/L mEqIL
days
days
Dogs with right-sided failure produced by tricuspid insufficiency and pulmonic stenosis
240
8.00
151
4.2
50
91
80
4.3
175
118
88
0.20
15.4
76
190
155
3.9
195
192
4.90
39.0
142
65
330
144
4.3
132
1.65
144
98
140
4.3
2.80
51
55
60
144
141
4.7
5.9
86
79
0.61
40
152
2.5
137
3.9
86
68
3.00
149
4.3
275
68
69
3.50
205
152
4.7
1.4
88
85
3.70
32.6
3.5
165
74
68
147
0.01
180
148
71
50.5
3.8
0.10
75
147
4.2
65
199
2.59
19.0
89.2
98.2
C
LVEDP*
E
mm water
95
81
119
75
108
96
28
42
67
99
55
65
108
66
Dog with naturally occurring right- and left-sided heart failure
1
41.0
1
2
3
17.9
18.0
22.0
150
1.20
153
3.6
230
210
280t
75
75
63
Dogs with constriction of the thoracic inferior vena cava
*
92
74
166
88
61
165
3.00
4.50
2.50
1.9
7.5
0.6
143
144
140
4.1
3.8
4.7
1751
165$
LVEDP is the abbreviation for left ventricular end-diastolic presst
are abbreviations for control and experimental, respective
t C and E
-: Inferior vena caval pressures instead of right atrial pressures.
KCl. The solution of myosin was diluted to 0.6 M KCl
and enough 0.6 M KCl was added to make 100 cc.
Potassium carbonate was added to adjust the pH to 7.5
and the solution was stirred overnight with a magnetic
stirrer. The preparation was centrifuged at 16,500 rpm
for 30 minutes, in the Lourdes centrifuge. The myosin
was precipitated for the second time by adding again 10
volumes of glass distilled water to each volume of myosin
solution. The myosin was allowed to settle and the
supernatant was siphoned off and discarded. The myosin
solution was centrifuged at 8,000 rpm for 10 minutes.
The residue was dissolved in 2.4 M KCl, diluted to 0.6 M
KCl and sufficient 0.6 M KCl was added to make 100 cc.
The pH was adjusted to 7 with potassium carbonate.
The solution was diluted to 0.3 M and centrifuged at
8,000 rpm for 10 minutes in the Lourdes centrifuge. The
third precipitation was carried out by further dilution to
a 0.06 M solution. The myosin solution was allowed to
settle overnight. The supernatant was siphoned off and
the remainder was centrifuged at 8,000 rpm for 10 minutes. The residue was dissolved in 2.4 M KCl and the
concentration was adjusted to 0.6 M KCl. The myosin
preparation was centrifuged at 16,500 rpm for 30 minutes
in the Lourdes centrifuge. The supernatant myosin solution was decanted from the pellet and centrifuged in a
Spinco model L ultracentrifuge for 4 hours at 30,000 rpm.
The final myosin solution was decanted from the pellet.
The yields ranged from 75 to 200 mg per 100 g of cardiac
muscle.'
1 No attempt was made to compare the yields of myosin
from normal and failing cardiac muscle. The aim of the
extraction procedure was to achieve purity of preparation
and the large losses of myosin which occurred would
make any attempt at quantitation meaningless.
Measurements of sedimentation velocity of cardiac
myosin were made with a Spinco model E analytical
ultracentrifuge. Two samples were centrifuged simultaneously by use of a wedge cell and a plain cell. Either
two different concentrations of myosin or one concentration of myosin with added ATP and MgCl2 and the same
preparation and concentration of myosin without these
compounds were centrifuged. The final concentrations of
ATP and MgCl2 were 5 X 10' M and 10' M, respectively. Kel F centerpieces were used to prevent denaturation of the protein. Ultracentrifugation 2 was performed
at 59,780 rpm or 250,000 G at a temperature of 70 C;
the bar angle was 600. Actual sedimentation constants
were corrected to 20° C and to water as a solvent by the
standard formula (15). A value of 0.728 was used for
the partial specific volume of myosin.
Diffusion measurements were made in an Aminco
model B electrophoresis apparatus at 6° C, using carefully
selected cells and the Raleigh interferometer in the manner described by Longsworth (16). The myosin solutions were dialyzed for 18 to 20 hours against 0.6 M KCl
buffered to pH 7.6 with phosphate. Diffusion coefficients
were corrected to 200 C and to water as a solvent. Sedimentation constants were determined on all but one of the
myosin preparations used for diffusion measurements.
Viscosity was measured with a size II Ubbelohde
viscosimeter with an outflow time for 0.6 M KCl of 100
seconds. All viscosity measurements on myosin were
made within the first day or two after completion of the
2 Slight variation in the Saow has been reported with
different rotor speeds (3). Ultracentrifugation was performed at 59,780 rpm because measurements are more
accurate with this rotor speed than with slower rates of
sedimentation for large molecules such as myosin (3, 15).
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CARDIAC MYOSIN AND HEART FAILURE
preparation. Myosin was dissolved in 0.6 M KCl and
measurements were made in a constant temperature water
bath at 22.50 ± 0.02° C. Multiple determinations on a
myosin preparation were made by repeated dilution of the
myosin solution and subsequent measurement of the viscosity. The relative viscosity ('reI) was determined as
the ratio of the outflow time for the solution of myosin to
that of 0.6 M KCl; 77, is equal to 77relr.
The protein concentration of the myosin solutions was
determined by micro-Kjeldahl analysis.
1465
vided a control for evaluation of possible changes
in failing heart muscle which might be secondary
to altered electrolyte or protein metabolism. Data
on their physiological state are presented in Table
I. An additional finding of interest in these animals is the presence of both right and left ventricular atrophy which has been reported elsewhere
(13).
Sedimentation velocity studies of myosin. The
sedimentation of myosin was observed in enzyme
RESULTS
preparations made from the combined right and
Physiological studies of experimental animals. left ventricles of normal dogs. Myosin from sepaThe results are presented in Table I. The 11 dogs rate right and left ventricles of dogs with right
with tricuspid insufficiency and pulmonic stenosis heart failure secondary to tricuspid insufficiency
showed evidence of pure right-sided congestive and pulmonic stenosis was studied while left venfailure. Mean right atrial pressure was markedly tricular myosin only was obtained from dogs with
elevated in every instance, whereas left ventricular constriction of the thoracic inferior vena cava. In
end-diastolic pressure was normal. Ascites was addition, studies were made on myosin from the
present in all dogs but Na excretion varied from left ventricle of a dog with naturally occurring
1.4 to 50.5 mEq per day. The ratio of right right- and left-sided failure.
Qualitatively the sedimentation patterns were
ventricular to left ventricular weight was 0.93 in
comparison with the normal value of 0.51 (13) identical for myosin from all sources of cardiac
(p < 0.001). Other previously reported data muscle. The typical sedimentation pattern con(13) on heart and lung weights in dogs with sisted of a single peak which suggested homocardiac failure secondary to tricuspid insufficiency geneity of the myosin preparation (Figure 1). In
and pulmonic stenosis showed no evidence of left a few instances, a very small boundary which
ventricular failure or hypertrophy. The average sedimented faster than the principal myosin comduration of life after the second operation (produc- ponent was observed. The magnitude of this
tion of pulmonic stenosis) was 98 days, whereas boundary was not sufficient to produce sedimentation constants which were different from those
the average duration of ascites was 89 days.
The one animal with naturally occurring conges- obtained in myosin preparations with only one
tive heart failure showed evidence of both right sedimentation boundary. Addition of ATP imand left ventricular hypertrophy and failure. The mediately before centrifugation did not influence
filling pressures in both the right and the left heart the sedimentation pattern or rate of movement of
were elevated. The heart was massively enlarged myosin (Figure 1).
Quantitative data on sedimentation velocity are
and weighed 502 g. The lungs weighed almost 2.5
times the average normal value of 9.15 + 1.30 g presented in Figure 2. The S20o, at zero concenper kg (13) and showed microscopic evidence of tration for myosin from normal heart muscle was
chronic passive congestion. The liver showed evi- 6.17 x 10-13 seconds. The slopes of the least
dence histologically of chronic congestion and squares straight lines and the y intercepts (Figure
presented the characteristic nutmeg appearance 2) for the myosin from failing right or left vengrossly.
tricles, from the nonfailing left ventricle of dogs
In addition to the normal animals, three dogs with tricuspid insufficiency and pulmonic stenosis,
with thoracic caval constriction and chronic ascites
left ventricle of dogs with
provided control material. These animals were and from the atrophic
not in cardiac failure but they showed essentially thoracic caval constriction were not statistically
the same alterations in salt and water metabolism different from the values for normal cardiac myoand the protein depletion observed in experimental sin. Both the slope of the line and the y intercept
heart failure (11-13). Consequently, cardiac for myosin from the left ventricle of dogs with
muscle from the dogs with caval constriction pro- tricuspid insufficiency and pulmonic stenosis were
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1466
DAVIS, CARROLL, TRAPASSO AND YANKOPOULOS
FIG. 1. ULTRACENTRIFUGAL SEDIMENTATION PATTERNS OF CARDIAC MYOSIN. Centrifugation
was carried out at 59,780 rpm; bar angle was 600. In A, cardiac myosin (approximately 3.0
mg per ml) from a normal dog in upper part of picture (wedge cell) and the same preparation
with added ATP in the lower picture (regular cell); photograph taken at 52 minutes after
reaching maximal speed. In B, two concentrations (1.5 and 1.0 mg per ml) of cardiac myosin
from a normal dog after completion of diffusion measurements; picture taken after 72 minutes
at a speed of 59,780 rpm. In C and D, cardiac myosin in concentrations of 0.9 and 2.5 mg per
ml from a dog with experimental congestive heart failure secondary to tricuspid insufficiency
and pulmonic stenosis; photograph in C was taken 12 minutes after reaching maximal speed
while picture in D was taken after 68 minutes.
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1467
CARDIAC MYOSIN AND HEART FAILURE
LV-THORACIC IVC
LV + RV- NORMAL
.0
6
S
20,W
CONSTRICTION
7
7
x
5
_
4
Ie
6
v_
5_
20w 4
&
3
2
2
0
I
2
3
5
4
O.0
6
MYOSIN MGI/ML
3
4
MG
MYOSIN
/ML
1
2
~~~~RV-FAILURE *&*
LV-FAILUREw
7
6
5
5
20W
3
2F
0
1
2
3
5
4
MYOSIN MG/ ML
FIG. 2. SEDIMENTATION CONSTANTS
PLOTTED AGAINST THE PROTEIN CONCENTRATION.
(Sw,)
I
6
1
2
3
MYOSIN MG /ML
FOR MYOSIN FROM FOUR DIFFERENT SOURCES
Each symbol represents myosin from a different
preparation. Right ventricular failure was secondary to tricuspid insufficiency and pulmonic
stenosis. Left ventricular failure was present in the one dog with naturally occurring cardiac
failure. RV and LV are abbreviations for right ventricle and left ventricle, respectively. The
weighted least squares straight lines are drawn for each group.
significantly greater (p < 0.01) than those for
myosin from the failing heart.
Diffusion measurements on myosin. Data on
the rates of diffusion of myosin from normal
cardiac muscle and from cardiac muscle of dogs
with cardiac failure are presented in Figure 3.
Extrapolation of the D20,w to zero concentration
for normal cardiac myosin yields a value of 1.1
x 10-7 cm2 per second.
No differences are apparent in the rates of diffusion of myosin from
the normal and experimental material.
Evidence of heterogeneity of the myosin preparations was obtained from analysis of the normalized fringe distances [see Longsworth (16)] at
different levels in the diffusing boundary. Maximum deviation of these distances was about 12
per cent, indicating variations of average diffusion
coefficients of at least 25 per cent. This indication
of polydispersity was apparent in myosin solutions
from both normal and experimental hearts.
Viscosity measurements. The viscosity of myosin was measured in enzyme preparations from
the combined right and left ventricular masses of
normal dogs, from separate right and left ventricles of dogs with right-sided failure secondary
to tricuspid insufficiency and pulmonic stenosis,
and from the left ventricle only of dogs with
thoracic caval constriction. The results are presented in Figure 4 where 78p/C is plotted against
the concentration of myosin. For normal cardiac
myosin, an excellent linear relation between 7sp/C
and concentration with evidence of concentration
dependence is present between concentrations of
3.5 and 0.4 mg per ml. In the very dilute solutions of myosin (below 0.4 mg per ml), the results
varied among different enzyme preparations. With
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1468
DAVIS, CARROLL, TRAPASSO AND YANKOPOULOS
I
I
I
I
I
A RV+LV-NORMAL
* RV-TI +PS
o LV-TI+PS
o LV- NATURAL CHF
1.8 F
1.4
D2ow10
1.0
cP
AA
*-I
*
At
oA
A
.
o
.6
.2
I
1
I
I
3
I
2
I
5
4
6
MYOSIN (mg /ml)
FIG. 3. DIFFUSION COEFFICIENTS ( D.,,,,) FOR MYOSIN PLOTTED AGAINST PROTEIN
CONCENTRATION. The symbols * and Li1 are for myosin from failing ventricular
muscle, whereas A and 0 represent myosin from normal muscle and from nonfailing
left ventricle of dogs with tricuspid insufficiency (TI) and pulmonic stenosis (PS),
respectively. CHF is the abbreviation for congestive heart failure.
The viscosity of myosin from the right ventricle
of dogs with right-sided congestive failure did not
appear to differ from myosin from normal dogs or
dogs with caval constriction. Both myosin from
the right ventricle and myosin from the left ventricle of dogs with right heart failure secondary
to tricuspid insufficiency and pulmonic stenosis
showed an increase in viscosity at low concentrations. Also, one myosin preparation from the left
one myosin preparation, the 9,p/C fell almost to
zero, whereas in two other preparations 7q8p/C increased. If this peculiar behavior at low concentrations is neglected, the intrinsic viscosity (sjp/C
at zero concentration) is 1.8. Cardiac myosin
from dogs with thoracic caval constriction provided another source of control material (Figure
4); the peculiar viscosity values at very low concentrations were again observed.
I
I
8
8 _
NORMAL
RIGHT- SIDED CONGESTIVE HEART FAILURE
7
7
6
6
5
5
"7sP
RV O°
LV '9
6
_ 5
-
4 .3
A
_x
,F
,
a
*
x
3 -adA& eA
ox
a
0A
4
A
0
at
2
2
A
x, A~,
t
IF
j
I
THORACIC IVC CONSTRICTION
7
I
-
oni
2
AA&
A
A
.
6 a
A
2
A
A
A
l
0
.5
1
L5
2
2.5
3
3.5
0
MYOSIN(mg /ml)
FIG. 4. SPECIFIC VISCOSITY/CONCENTRATION
.5
1.5
2
2.5
MYOSI N (mg /mL)
(-q.,/C)
3
3.5
0
.5
1
1.5
2
2.5
3
35
MYOSIN (mg /ml)
OF MYOSIN PLOTTED AGAINST THE PROTEIN CONCENTRATION.
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CARDIAC MYOSIN AND HEART FAILURE
1469
ventricle of a dog with right heart failure gave myosin. They suggested that myosin is a rod
similar response to one myosin preparation from 1,620 A long and 26 A thick. If myosin preparaa normal heart in that qp/C decreased progrestions which yield values of approximately 500,000
for the molecular weight consist mostly of dimers,
sively at very low myosin concentrations.
it appears that the two monomers of myosin are
DISCUSSION
arranged end-to-end to form a dimer. In this
The present physicochemical measurements of event, the molecular dimensions described by Holtcardiac myosin have yielded results very similar zer and Lowey (7) would apply to the dimer.
to those reported for skeletal muscle myosin
Another similarity between the present cardiac
(1-7). There is good agreement (3-7) that the myosin preparation and skeletal muscle myosin is
S20,w for skeletal muscle myosin is in the range the occurrence of polydispersity. The diffusion
of 6.15 to 6.40 x 1013 seconds. Laki and Carroll data in this study provide evidence for a poly(4) obtained a value of 1.0 x 10-7 cm2 per second disperse system from analysis of the normalized
for the diffusion coefficient of skeletal myosin. If fringe distances at different levels in the diffusing
the peculiar viscosity behavior at concentrations boundary. In the ultracentrifuge patterns, the
below 0.4 mg per ml is neglected, the present occasional presence of a small sedimentation commeasurements of the intrinsic viscosity of cardiac ponent which moved faster than the principal
myosin from normal hearts show a value of 1.8 sedimenting boundary is probably a reflection of
which is similar to that reported by others (1, 2, polymerized myosin. Aggregation of the basic
7) for skeletal muscle myosin. Calculations of the myosin monomer, with the resultant appearance of
molecular weight of cardiac myosin from normal a fast-moving component during ultracentrifugaheart muscle, from the present S20,w of 6.17 x 10-13 tion, has been observed for skeletal muscle myosin
seconds and the diffusion coefficient of 1.1 x 10-7 (7, 17).
cm2 per second, give a value of 501,000. However,
The present viscosity measurements of cardiac
the scatter of sedimentation and diffusion con- myosin showed a peculiar finding in very dilute
stants is sufficient to include values from 450,000 solutions (below 0.5 mg per ml). The q)8p/C into 550,000 for the molecular weight.
creased markedly in some preparations and deAlso, the findings in this study are in excellent creased in others. The phenomenon occurred with
agreement with the results of Gergely and Kohler myosin from both normal and failing hearts and
(9) from studies of normal cardiac myosin. They with cardiac myosin from dogs with thoracic caval
obtained a value of 500,000 for the molecular constriction. Similar changes in the viscosity of
weight from light scattering measurements. The cardiac myosin at low concentrations have been
present data and those of Gergely and Kohler ap- reported previously by Olson (8). In view of the
pear to be at variance with the finding of Olson the irreproducibility of the viscosity measurements
(8) of a value of 223,000 for normal cardiac among different myosin preparations from the
myosin. However, the results from all three lab- same sources of material (normal or failing venoratories would be reconcilable if Olson's myosin tricle), the possibility must be considered that
preparations consisted of monomers, whereas the viscosity measurements at very low concentrations
cardiac myosin prepared by Gergely and Kohler do not represent the true viscosity of the solution.
and the present preparations consisted mostly of It does not seem likely that the viscosity changes at
low concentrations were the result of the temperamyosin in the form of dimers.
The close similarity of the magnitude of the ture (22.5° C) at which viscosity was measured,
parameters from the present data on cardiac my- since Olson (8) observed the same peculiar visosin to those of Holtzer and Lowey (7) and others cosity at 10 C. Also, Holtzer and Lowey (7) con(2-6) for skeletal myosin suggests that the shape cluded that the slight difference in intrinsic visof the cardiac myosin molecule is very similar, if
cosity of myosin measured at 10 and at 260 C was
not identical, to that for skeletal myosin. From probably not significant.
sedimentation, viscosity and light scattering measThe results of this study show no difference
urements, Holtzer and Lowey (7) reported a between cardiac -myosin from normal dog hearts
molecular weight of 493,000 for skeletal muscle and from either the right, or left ventricle of dogs
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1470
DAVIS, CARROLL, TRAPASSO AND YANKOPOULOS
with right-sided congestive failure secondary to tricuspid insufficiency and pulmonic stenosis. Also,
left ventricular myosin from the one dog with
naturally occurring right and left ventricular failure appeared normal. These findings are in contrast to the results of Olson (8) who reported that
an abnormal cardiac myosin was extracted from
the combined right and left ventricles of dogs with
tricuspid insufficiency and pulmonic stenosis. Olson and Piatnek (18) reported that their dogs
with tricuspid insufficiency and pulmonic stenosis
were in left ventricular failure.
In the present study, cardiac myosin was obtained from separate right and left ventricles of the
animals with cardiac failure. This procedure was
adopted so that myosin from the specific failing
chamber (right or left ventricle) could be compared with normal material. There was no evidence for left ventricular failure in the present
dogs with tricuspid insufficiency and pulmonic
stenosis, and an earlier more extensive study (13)
also revealed pure right-sided cardiac failure in
dogs with tricuspid insufficiency and pulmonic
stenosis.
It has been suggested by Benson (19) that
actomyosin is partially fragmented into uncombined myosin and actin in dogs with experimental
cardiac failure secondary to tricuspid insufficiency
and pulmonic stenosis. However, recent extensive
studies of cardiac actomyosin (10) have failed to
confirm the findings of Benson. Sedimentation
velocity and viscosity measurements of cardiac
actomyosin from the right ventricle of dogs with
chronic experimental congestive failure, produced
by either tricuspid insufficiency and pulmonic
stenosis or by severe pulmonic stenosis alone,
showed no evidence for altered actomyosin in 7 of
11 dogs. In the other four animals, a slow sedimenting component was present in the sedimentation diagrams but this appeared to be a preparation
or extraction artifact. The present observations
and those reported previously on actomyosin (10)
offer no support for the view that altered contractile proteins constitute the biochemical defect
in the failing heart.
SUMMARY AND CONCLUSIONS
The molecular weight of cardiac myosin was
determined from sedimentation and free diffusion
data; a value of approximately 500,000 was obtained for normal cardiac myosin. Measurements
of the intrinsic viscosity of cardiac myosin from
normal hearts showed a value of 1.8. Sedimentation velocity, viscosity and diffusion measurements
of myosin showed no differences between myosin
prepared from normal hearts and myosin obtained
from failing ventricular muscle. Also, the present
physicochemical constants for cardiac myosin are
in good agreement with data described by others
for skeletal muscle myosin.
ACKNOWLEDGMENT
We are grateful to Dr. Samuel Greenhouse and Mrs.
Norma French for statistical analysis of the data.
REFERENCES
1. Szent-Gyorgyi, A. The Chemistry of Muscular Contraction, 2nd ed. New York, Academic Press,
1951.
2. Portzehl, H., Schramm, G., and Weber, H. H.
Aktomyosin und seine Komponenten. Z. Naturforsch. 1950, 5b, 61.
3. Parrish, R. G., and Mommaerts, W. F. H. M. Studies on myosin. II. Some molecular-kinetic data.
J. biol. Chem. 1954, 209, 901.
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